Du Hui, Chen Min, Zhang Ying, Zhao Ming-Hui
Renal Division and Institute of Nephrology, Peking University First Hospital, Beijing, 100034, People's Republic of China.
J Clin Immunol. 2006 Mar;26(2):138-44. doi: 10.1007/s10875-006-9004-8. Epub 2006 Apr 18.
Lupus nephritis (LN) is a prototypic autoimmune disease, however, the precise immuno-pathogenesis of LN remains to be elucidated. In our previous studies, autoantibodies against mesangial cells had been identified in sera from patients with lupus nephritis and could bind the membrane proteins of human mesangial cells (HMC) directly through antigen-antibody interaction without DNA bridge. The current study is to investigate whether the autoantibodies were associated with anti-DNA antibodies and their target antigens distribution in different cell types. Sera from nine patients with renal biopsy proven lupus nephritis with positive anti-dsDNA antibodies and four healthy subjects were collected. IgG was isolated by Protein G affinity chromatography and then non-DNA-binding IgG fractions were obtained after deletion of anti-DNA antibodies using a DNA-cellulose affinity column. Membrane proteins, obtained from HMC, human umbilical vein endothelial cells (HUVEC), peripheral mononuclear cells by sonication and sequential centrifugation, were solubilized and applied in Western-blot analysis to characterize the target antigens. In results, the non-DNA-binding IgG fractions from sera of patients with lupus nephritis could blot the protein(s) of HMC membrane at 74, 63, and 42 kD. However, only a similar 74-kD protein could be blotted on membrane of HUVEC, and the target antigens on membranes of mononuclear cells were heterogeneous. In conclusion, our preliminary study had demonstrated that non-DNA binding autoantibodies against mesangial cells could be found in sera from patients with lupus nephritis. Although the target antigens might not be cell specific, the roles of these autoantibodies in the pathogenesis of lupus nephritis need further investigation.
狼疮性肾炎（LN）是一种典型的自身免疫性疾病，然而，LN确切的免疫发病机制仍有待阐明。在我们之前的研究中，已在狼疮性肾炎患者的血清中鉴定出抗系膜细胞自身抗体，这些抗体可通过抗原 - 抗体相互作用直接结合人系膜细胞（HMC）的膜蛋白，而无需DNA桥接。本研究旨在调查这些自身抗体是否与抗DNA抗体相关，以及它们在不同细胞类型中的靶抗原分布情况。收集了9例经肾活检证实为狼疮性肾炎且抗双链DNA抗体阳性的患者血清以及4例健康受试者的血清。通过蛋白G亲和层析法分离IgG，然后使用DNA - 纤维素亲和柱去除抗DNA抗体后获得非DNA结合IgG组分。通过超声处理和连续离心从HMC、人脐静脉内皮细胞（HUVEC）、外周单个核细胞中获得膜蛋白，将其溶解并应用于蛋白质印迹分析以鉴定靶抗原。结果显示，狼疮性肾炎患者血清中的非DNA结合IgG组分可使HMC膜上74、63和42 kD的蛋白出现印迹。然而，在HUVEC膜上仅能使一种类似的74 kD蛋白出现印迹，且单个核细胞膜上的靶抗原具有异质性。总之，我们的初步研究表明，狼疮性肾炎患者血清中可发现针对系膜细胞的非DNA结合自身抗体。尽管靶抗原可能并非细胞特异性的，但这些自身抗体在狼疮性肾炎发病机制中的作用仍需进一步研究。
